Some implantable medical devices, such as implantable drug pumps, include fluid reservoirs that may be accessed through ports, which may be self-sealing. The medical device may be configured to deliver a therapeutic agent from the fluid reservoir to a patient according to a therapy program, which may, for example, specify the size of a bolus delivered to the patient, the concentration of the therapeutic agent, and/or the delivery rate of the therapeutic agent. After the medical device is implanted within a patient, it may be desirable to percutaneously access the reservoir of the implanted medical device in order to refill the reservoir with a therapeutic agent, flush out the reservoir or change the fluid in the reservoir.